正辛烷的高压拉曼光谱研究

Raman Scattering Studies of n-Octane under High Pressure

采用金刚石对顶砧高压装置,在室温下对正辛烷(C8H18)进行了原位高压拉曼光谱研究,实验的最高压力为13 GPa。在实验的压力范围内,正辛烷的拉曼峰位随压力的升高均向高频移动,峰强逐渐减弱,峰形变宽。常态为液态的正辛烷在0.8 GPa时,拉曼频移随压力的变化曲线出现了拐点,发生了液-固相变;在6.8 GPa时,伴随着原拉曼峰的消失或劈裂,以及新拉曼峰的出现,此时正辛烷可能发生了固-固相变。该相变压力低于已有的低碳数正烃烷的压致相变结果。正烃烷的压致相变压力点,具有随着结构链长的增加,其相变压力降低的规律。

High pressure Raman spectra of n-octane were investigated by diamond anvil cell（DAC） at pressure up to 7 GPa and ambient temperature.The result shows that the liquid-solid phase transition of n-octane takes place around 0.8 GPa.Within the experimental pressure range,the Raman shift of n-octane moves to higher frequency,while the peak intensity decreases,and the width of peaks broaden with increasing pressure.A turning point is observed in the curve of pressure-dependent Raman shift when the pressure increases up to 6.8 GPa.This result indicates that a solid-solid phase transition for n-octane has been finished at this pressure.The pressure-induced phase transition pressure in alkanes decreases with the length of their chains increasing.